To address the challenges associated with methane gas leak monitoring and localization in oil and gas pipelines, and to overcome the limitations of existing laser-based point measurement techniques, this study proposes a novel dual-band short-wave infrared (SWIR) gas detection technology based on differential ratio spectral imaging. The system locks the laser output at a central wavelength specific to methane detection and controls the laser beam scanning trajectory and direction in real time through an adjustable beam scanning module. By integrating laser absorption spectroscopy with a shortwave infrared camera, spectral information from both absorption and non-absorption regions is captured to generate intensity images of methane gas at varying volume fractions under specific laser wavelengths. Through the application of image processing algorithms, differential ratio analysis is conducted between the methane absorption band (1653.72 nm) and two adjacent non-absorption bands (1653.82 nm and 1653.62 nm), effectively eliminating background radiation interference in methane gas plumes and distinctly visualizing the intensity distribution of methane volume fractions. Experimental validation using standard gas bags to simulate methane leak scenarios demonstrates the feasibility of this approach, with processed image intensity to establish a calibration curve correlating the dual-band differential ratio with gas concentration path length, enabling quantitative detection and analysis. This imaging methodology effectively mitigates the drawbacks of conventional measurement techniques, such as measurement point deviation and the inability to achieve quantitative assessment, thereby providing a robust and precise approach for applications including methane cloud distribution mapping in mining operations and methane leak detection in oil and gas fields.